There has been a growing interest in a magnetic random access memory (MRAM) using the magnetoresistance effect of a ferromagnetic body as a next-generation solid-state nonvolatile memory capable of performing high-speed reading/writing, large-capacity, and low-power consumption operations.
However, with increasing integration of magneto tunnel junction (MTJ) elements to realize gigabit (GBit)-level MRAM, there arises a problem of an increasing write/erase current necessary to write data to the MTJ element or erase data from the MTJ element. A write/erase current may be denoted simply as a write current below and a write/erase operation may be denoted simply as a write operation.
When heat generated by the write/erase current (hereinafter, referred to as current-carrying heat) is conducted to a non-selected MTJ element, the spin of the non-selected MTJ element is reversed, causing an erroneous write (disturb). Thus, preventing thermal conduction of current-carrying heat to a non-selected cell or reducing the write current as a source thereof is demanded.
Further, if current-carrying heat remains for a long time in a selected cell after a write operation, a problem of a reduced writing speed is caused. Thus, after a write operation is performed, it is necessary to dissipate current-carrying heat from a selected cell as soon as possible.
In recent years, on the other hand, research of MRAM in a write mode that reverses only the magnetization direction of a recording layer of an MTJ element by using heat assistance by the current-carrying heat into a storage cell is conducted.
In conventional MRAM, as described above, there has been a problem of a reduced writing speed due to an occurrence of erroneous writing caused by current-carrying heat.